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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 279 of 326

This practice set contains high-yield board review questions covering key concepts in 3. Adult Reconstruction (Hip & Knee). Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 5561

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old patient falls and sustains a periprosthetic femur fracture around a cemented THA stem. Radiographs demonstrate a fracture around the tip of the stem. The stem demonstrates gross subsidence and lucencies at the cement-bone interface, and the proximal femur has extremely thin cortices with significant osteolysis. What is the Vancouver classification and the recommended treatment?

. Vancouver B1: Open reduction internal fixation with cerclage cables
. Vancouver B2: Revision to a standard long cementless stem
. Vancouver B3: Proximal femoral replacement or modular tapered stem revision
. Vancouver C: Open reduction internal fixation with a lateral locking plate
. Vancouver A: Trochanteric fixation

Correct Answer & Explanation

. Vancouver B1: Open reduction internal fixation with cerclage cables

Explanation

This is a Vancouver B3 fracture. The fracture occurs around the stem (Type B), the stem is loose (distinguishing it from B1), and there is poor proximal bone stock (distinguishing it from B2). The standard of care for a B3 fracture in an elderly patient is revision using a proximal femoral replacement (tumor prosthesis) or a modular fluted tapered stem, bypassing the fracture to gain distal fixation.

Question 5562

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total hip arthroplasty utilizing the direct lateral (Hardinge) approach, the surgeon performs a longitudinal split in the gluteus medius. If this split extends more than 5 cm proximal to the tip of the greater trochanter, which of the following nerves is at greatest risk of iatrogenic injury?

. Superior gluteal nerve
. Inferior gluteal nerve
. Sciatic nerve
. Femoral nerve
. Lateral femoral cutaneous nerve

Correct Answer & Explanation

. Superior gluteal nerve

Explanation

The superior gluteal nerve runs approximately 3 to 5 cm proximal to the tip of the greater trochanter. In the direct lateral approach (Hardinge), the split in the gluteus medius must not exceed 5 cm proximal to the trochanter to avoid denervating the anterior portion of the gluteus medius and the tensor fasciae latae, which would result in a postoperative Trendelenburg gait.

Question 5563

Topic: Total Knee Arthroplasty (TKA)

Which of the following statements best describes the core principle of 'kinematic alignment' in total knee arthroplasty, as opposed to traditional 'mechanical alignment'?

. Restoring the mechanical axis to 0 degrees relative to the weight-bearing line
. Aligning the femoral component strictly parallel to the surgical transepicondylar axis
. Restoring the patient's individual pre-arthritic joint lines and kinematic axes
. Routinely externally rotating the femoral component by 3 degrees
. Releasing collateral ligaments heavily to create equal rectangular gaps

Correct Answer & Explanation

. Restoring the mechanical axis to 0 degrees relative to the weight-bearing line

Explanation

Kinematic alignment aims to position the TKA components such that they restore the patient's native, pre-arthritic joint line and the three kinematic axes of the knee. This is in contrast to mechanical alignment, which seeks to create a neutral mechanical axis (0 degrees) with cuts perpendicular to the mechanical axes of the femur and tibia, often necessitating soft tissue releases.

Question 5564

Topic: Total Hip Arthroplasty (THA)

A patient with a primary THA complains of recurrent posterior dislocations. Component analysis via advanced imaging reveals that the acetabular cup is positioned in 20 degrees of abduction and 0 degrees of anteversion. What is the most appropriate primary surgical strategy to address this instability?

. Revise the acetabular cup to increase abduction
. Revise the acetabular cup to increase anteversion
. Revise the femoral stem to increase offset
. Perform a greater trochanteric advancement
. Exchange the liner for a constrained design without changing cup position

Correct Answer & Explanation

. Revise the acetabular cup to increase abduction

Explanation

The "safe zone" for acetabular cup placement, historically described by Lewinnek, is 40±10 degrees of abduction and 15±10 degrees of anteversion. A cup with 0 degrees of anteversion is retroverted (or neutral), which highly predisposes the patient to posterior dislocation. The most appropriate surgical strategy is revising the cup to increase anteversion to within the safe zone.

Question 5565

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old female presents with persistent pain, diffuse swelling, and stiffness 1 year after a standard primary TKA. Infection workup, including inflammatory markers and aspiration, is completely negative. Radiographs show no loosening. She has a documented history of severe contact dermatitis to cheap jewelry. Which metal is the most common cause of hypersensitivity reactions in patients with orthopedic implants?

. Cobalt
. Chromium
. Titanium
. Nickel
. Vanadium

Correct Answer & Explanation

. Cobalt

Explanation

Nickel is the most common metal sensitizer in the general population (up to 15% prevalence) and the most frequent culprit in suspected metal hypersensitivity reactions following total joint arthroplasty. Most standard femoral components in TKA are made of Cobalt-Chromium alloys, which contain trace amounts of Nickel.

Question 5566

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following is widely considered an absolute contraindication to a medial unicompartmental knee arthroplasty (UKA)?

. Age greater than 60 years
. Body Mass Index greater than 30
. Anterior cruciate ligament (ACL) deficiency
. Inflammatory arthropathy
. Isolated medial compartment osteoarthritis

Correct Answer & Explanation

. Age greater than 60 years

Explanation

Inflammatory arthropathy (e.g., rheumatoid arthritis) is an absolute contraindication for UKA because it is a systemic disease that involves the entire joint. If UKA is performed, the disease will inevitably destroy the preserved compartments. Age, BMI, and ACL deficiency were historically absolute contraindications but are now considered relative or addressable by some surgeons.

Question 5567

Topic: 3. Adult Reconstruction (Hip & Knee)

In a patient undergoing revision THA for aseptic loosening with severe acetabular bone loss, which of the following radiographic findings is pathognomonic for pelvic discontinuity?

. Medial migration of the cup past Kohler's line
. Osteolysis of the ischial tuberosity
. A visible fracture line traversing the anterior and posterior columns separating the superior and inferior hemipelvis
. Superior migration of the hip center of rotation by 3 cm
. A broken inferior pubic ramus

Correct Answer & Explanation

. Medial migration of the cup past Kohler's line

Explanation

Pelvic discontinuity is defined as a complete separation of the superior hemipelvis (ilium) from the inferior hemipelvis (ischium and pubis) due to bone loss or fracture through both the anterior and posterior columns. While medial migration past Kohler's line indicates protrusio, a visible fracture traversing both columns is pathognomonic for discontinuity.

Question 5568

Topic: 3. Adult Reconstruction (Hip & Knee)
A 70-year-old male is 6 weeks post-operative from a primary TKA. He presents to the clinic with acute onset knee pain, erythema, and swelling over the past 3 days. A synovial fluid aspiration is performed. According to widely accepted consensus criteria, what synovial fluid white blood cell (WBC) count threshold is highly diagnostic of an acute periprosthetic joint infection (within 90 days post-op)?
. > 1,500 cells/μL
. > 3,000 cells/μL
. > 10,000 cells/μL
. > 25,000 cells/μL
. > 50,000 cells/μL

Correct Answer & Explanation

. > 10,000 cells/μL

Explanation

The diagnostic thresholds for periprosthetic joint infection (PJI) vary depending on the timing post-surgery. For chronic PJI, a synovial WBC > 3,000 cells/μL is diagnostic. However, in the acute post-operative setting (typically defined as < 90 days), the normal postoperative inflammatory response elevates cell counts, so the diagnostic threshold for acute PJI is set much higher, typically at > 10,000 cells/μL.

Question 5569

Topic: 3. Adult Reconstruction (Hip & Knee)
A 72-year-old female presents with severe groin pain 15 years after a primary total hip arthroplasty. Radiographs show a loose acetabular component with medial migration past the Kohler line, superior migration of 4 cm, and a visible fracture line through the acetabular fossa separating the superior and inferior hemipelvis. Which of the following is the most appropriate acetabular reconstruction strategy for this specific defect?
. Insertion of a jumbo hemispherical cup with multiple screws
. Impaction bone grafting with a cemented polyethylene cup
. Acetabular distraction utilizing a cup-cage construct or custom triflange
. Conversion to a bipolar hemiarthroplasty
. Girdlestone resection arthroplasty

Correct Answer & Explanation

. Acetabular distraction utilizing a cup-cage construct or custom triflange

Explanation

The clinical and radiographic findings describe a Paprosky Type IIIB acetabular defect with pelvic discontinuity (fracture through the acetabulum separating the superior and inferior hemipelvis). Standard hemispherical cups cannot achieve rigid fixation in the presence of pelvic discontinuity. The most reliable options for biological or mechanical bridging of the discontinuity include a cup-cage construct, a custom triflange component, or an acetabular distraction technique utilizing a highly porous trabecular metal implant to achieve stabilization and healing of the pelvic columns.

Question 5570

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male is evaluated for a painful total hip arthroplasty 2 years postoperatively. Serum CRP is 15 mg/L and ESR is 45 mm/hr. Hip aspiration yields synovial fluid with a WBC count of 2,800 cells/uL and 65% polymorphonuclear leukocytes (PMNs). According to the International Consensus Meeting (ICM) criteria, which of the following synovial fluid tests would provide the highest diagnostic specificity to confirm a periprosthetic joint infection?

. Synovial fluid leukocyte esterase strip test
. Synovial fluid alpha-defensin biomarker assay
. Synovial fluid C-reactive protein (CRP)
. Synovial fluid interleukin-6 (IL-6)
. Polymerase chain reaction (PCR) for Staphylococcal DNA

Correct Answer & Explanation

. Synovial fluid leukocyte esterase strip test

Explanation

According to the ICM criteria for periprosthetic joint infection (PJI), the synovial fluid alpha-defensin test is highly sensitive and specific (often >95% specificity) for diagnosing PJI. Alpha-defensin is an antimicrobial peptide released by neutrophils in response to infection. It is unaffected by prior antibiotic administration and is considered a major diagnostic criterion in the modern MSIS/ICM scoring systems for PJI.

Question 5571

Topic: 3. Adult Reconstruction (Hip & Knee)

In a posterior-stabilized (PS) total knee arthroplasty, the cam-post mechanism is designed to substitute for the function of the resected posterior cruciate ligament (PCL). What is the most common mechanical etiology for a posterior dislocation of the tibial polyethylene post mechanism over the femoral cam?

. An excessive and unbalanced flexion gap
. An excessive and unbalanced extension gap
. Oversizing of the femoral component
. Medial collateral ligament insufficiency
. Excessive anterior placement of the femoral component

Correct Answer & Explanation

. An excessive and unbalanced flexion gap

Explanation

Posterior dislocation of a PS knee (where the femoral component shifts anteriorly over the tibial post) typically occurs in deeper flexion. The most common cause is a loose (excessive) flexion gap relative to the extension gap. When the knee goes into flexion, the excessive laxity allows the femur to translate anteriorly or the tibia to translate posteriorly, reducing the 'jump distance' and allowing the femoral cam to jump over the tibial post.

Question 5572

Topic: 3. Adult Reconstruction (Hip & Knee)

A 45-year-old female undergoes a total hip arthroplasty utilizing a ceramic-on-ceramic bearing surface. One year postoperatively, she complains of a reproducible, audible squeaking noise during gait. Which of the following implant positioning factors is most strongly associated with the development of this phenomenon?

. Excessive femoral anteversion
. Acetabular component malposition leading to edge loading
. Use of an oversized femoral head (e.g., 40 mm)
. Increased lateral femoral offset
. Protrusio acetabuli placement of the cup

Correct Answer & Explanation

. Excessive femoral anteversion

Explanation

Squeaking in ceramic-on-ceramic (CoC) total hip arthroplasties occurs in 1-10% of cases. The primary biomechanical etiology is stripe wear and loss of fluid film lubrication secondary to 'edge loading'. Edge loading occurs when the joint contact mechanics shift to the rim of the acetabular liner, most commonly caused by malpositioning of the acetabular component (such as excessive steepness/abduction or excessive anteversion), or due to microseparation during the swing phase of gait.

Question 5573

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty, the surgeon assesses the gaps utilizing trial components. The knee demonstrates severe tightness in full extension preventing 0 degrees of extension, but demonstrates symmetric and appropriate ligamentous tension at 90 degrees of flexion. Which of the following is the most appropriate intraoperative adjustment to balance the knee?

. Downsize the femoral component
. Resect more bone from the distal femur
. Resect more bone from the proximal tibia
. Increase the posterior slope of the tibial resection
. Release the posterior cruciate ligament

Correct Answer & Explanation

. Downsize the femoral component

Explanation

This scenario describes a knee that is 'tight in extension and balanced in flexion.' The extension gap is controlled by the distal femoral cut and the proximal tibial cut, while the flexion gap is controlled by the posterior femoral cut and the proximal tibial cut. Since the flexion gap is perfectly balanced, altering the tibia would ruin the flexion gap. Therefore, to selectively enlarge the extension gap without affecting the flexion gap, the surgeon must resect more bone from the distal femur.

Question 5574

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old male undergoes a right total hip arthroplasty. Intraoperatively, the surgeon decides to utilize a high-offset femoral stem rather than a standard-offset stem of the same size. Which of the following best describes the fundamental biomechanical effect of this implant choice?

. It decreases the abductor moment arm and increases the joint reactive force.
. It increases the abductor moment arm and decreases the joint reactive force.
. It increases both the abductor moment arm and the joint reactive force.
. It increases leg length without altering the abductor moment arm.
. It medializes the femoral shaft relative to the center of rotation.

Correct Answer & Explanation

. It decreases the abductor moment arm and increases the joint reactive force.

Explanation

Increasing the femoral offset shifts the femur further laterally from the center of rotation of the hip joint. This increases the moment arm of the abductor muscles. Because the moment arm is longer, the abductor muscles require less force to maintain a level pelvis during single-leg stance. Since the joint reactive force (JRF) across the hip is primarily generated by the compressive force of the abductor muscles, decreasing the required abductor force directly decreases the JRF across the hip joint.

Question 5575

Topic: 3. Adult Reconstruction (Hip & Knee)

A 58-year-old male with a metal-on-metal total hip arthroplasty presents with a painless, palpable mass in the anterior groin and subjective hip stiffness. Serum inflammatory markers are within normal limits. Serum cobalt and chromium levels are elevated at 15 ppb. Which of the following is the most appropriate next step in the clinical evaluation of this mass?

. Fine-needle aspiration (FNA) of the mass
. Open incisional biopsy to rule out soft tissue sarcoma
. Metal artifact reduction sequence (MARS) MRI of the hip
. Radionuclide three-phase bone scan
. Computed tomography (CT) of the abdomen and pelvis with IV contrast

Correct Answer & Explanation

. Fine-needle aspiration (FNA) of the mass

Explanation

The clinical presentation is highly suspicious for an adverse local tissue reaction (ALTR) or aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL), often referred to as a 'pseudotumor', secondary to metal wear debris in a metal-on-metal hip. The gold standard imaging modality to characterize the size, extent, and nature of the periprosthetic soft-tissue mass or fluid collection is a Metal Artifact Reduction Sequence (MARS) MRI.

Question 5576

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty, the surgeon performs a trial reduction and observes severe lateral patellar maltracking with a tendency for the patella to dislocate laterally. The patellar component has already been medialized appropriately. Which of the following uncorrected component positioning errors is the most likely primary cause of this severe lateral maltracking?

. Internal rotation of the femoral component
. External rotation of the femoral component
. External rotation of the tibial component
. Excessive proximal placement of the patellar component
. Medialization of the femoral component

Correct Answer & Explanation

. Internal rotation of the femoral component

Explanation

Patellar maltracking in TKA is exquisitely sensitive to component rotation. Internal rotation of the femoral component medializes the trochlear groove, increasing the Q-angle and driving the patella laterally. Similarly, internal rotation of the tibial component lateralizes the tibial tubercle, which also increases the Q-angle and exacerbates lateral maltracking. Therefore, internal rotation of either the femoral or tibial components is a primary technical error leading to lateral patellar instability.

Question 5577

Topic: 3. Adult Reconstruction (Hip & Knee)
A 35-year-old male with a history of high-dose corticosteroid use presents with progressive, severe hip pain. AP and frog-leg lateral radiographs reveal sclerosis and cystic changes in the femoral head, accompanied by a distinct subchondral radiolucent line (crescent sign), but no frank flattening or collapse of the femoral head contour is visible. According to the Ficat and Arlet classification, what stage does this represent, and what is the generally accepted optimal surgical treatment?
. Stage II; Core decompression with or without bone grafting
. Stage III; Core decompression
. Stage III; Total hip arthroplasty
. Stage IV; Periacetabular osteotomy
. Stage I; Protected weight bearing and bisphosphonates

Correct Answer & Explanation

. Stage III; Total hip arthroplasty

Explanation

The presence of a 'crescent sign' represents a subchondral fracture, which denotes early structural collapse of the femoral head. In the Ficat and Arlet classification, a crescent sign and/or early flattening classifies the osteonecrosis as Stage III. Once subchondral collapse (Stage III) has occurred, joint-preserving procedures such as core decompression are generally ineffective. Total hip arthroplasty is the most reliable and indicated treatment for Ficat Stage III and IV osteonecrosis of the hip.

Question 5578

Topic: 3. Adult Reconstruction (Hip & Knee)

During a complex primary total knee arthroplasty for a severe fixed valgus deformity, the surgeon performs an extensive lateral release, including the IT band, LCL, and popliteus tendon. Following these releases, the flexion and extension gaps are symmetric in size, but there is persistent gross medial-lateral instability in both flexion and extension due to lateral side incompetence. The medial soft tissues remain intact and competently tensioned. Which of the following is the most appropriate implant constraint choice to ensure coronal stability?

. Fixed-bearing posterior-stabilized (PS) prosthesis
. Unicompartmental knee arthroplasty
. Varus-valgus constrained (VVC) non-hinged prosthesis
. Fully linked rotating hinge prosthesis
. Cruciate-retaining (CR) prosthesis with ultra-congruent polyethylene

Correct Answer & Explanation

. Fixed-bearing posterior-stabilized (PS) prosthesis

Explanation

A Varus-Valgus Constrained (VVC) or constrained condylar knee (CCK) implant features a tall, widened central post that fits tightly within the femoral box to provide substantial coronal stability. It is specifically indicated when there is deficiency of the LCL or an attenuated MCL that prevents balancing with standard soft-tissue releases, provided the remaining collateral envelope is somewhat intact or can be tensioned. A fully linked hinge is generally reserved for global collateral insufficiency (e.g., complete loss of both MCL and LCL or profound bone loss).

Question 5579

Topic: 3. Adult Reconstruction (Hip & Knee)

During a posterior (Kocher-Langenbeck) approach to the hip for a posterior wall acetabular fracture, the surgeon isolates and releases the short external rotators. To protect the primary extraosseous blood supply to the adult femoral head, the surgeon must exercise extreme caution when dissecting near the superior border of the quadratus femoris. Which specific vessel is at risk in this precise anatomic location?

. Inferior gluteal artery
. Deep branch of the medial femoral circumflex artery (MFCA)
. Ascending branch of the lateral femoral circumflex artery (LFCA)
. Artery of the ligamentum teres (foveal artery)
. First perforating branch of the profunda femoris

Correct Answer & Explanation

. Inferior gluteal artery

Explanation

The primary blood supply to the adult femoral head is the deep branch of the medial femoral circumflex artery (MFCA). This critical vessel courses posteriorly between the pectineus and iliopsoas, and then emerges posteriorly in the interval between the inferior gemellus and the superior border of the quadratus femoris. When performing a posterior approach to the hip, preserving the quadratus femoris (or at least its superior border) and carefully ligating vessels at the trochanteric bursa is essential to avoid transecting the deep branch of the MFCA and causing iatrogenic avascular necrosis.

Question 5580

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female presents with persistent, localized groin pain 1 year after an uncomplicated primary THA. The pain is strongly reproducible with resisted active hip flexion from a seated position. Radiographs reveal a well-fixed, cementless acetabular component with 25 degrees of anteversion and a prominent anterior edge overhanging the bone. Non-operative management, including physical therapy and a targeted corticosteroid injection, has failed. What is the most appropriate next step in surgical management?

. Arthroscopic or open release of the iliopsoas tendon.
. Revision of the acetabular component to reduce anteversion and overhang.
. Revision of the femoral stem to increase offset.
. Open debridement of the rectus femoris origin.
. Exchange of the femoral head to a smaller diameter.

Correct Answer & Explanation

. Arthroscopic or open release of the iliopsoas tendon.

Explanation

The patient is experiencing iliopsoas impingement, characterized by anterior groin pain exacerbated by resisted hip flexion (strait leg raise or sitting). A prominent anterior cup edge is a classic anatomical cause. When conservative measures (NSAIDs, PT, fluoroscopic/ultrasound-guided steroid injections into the psoas sheath) fail, iliopsoas tendon release (either arthroscopic or open) is the most appropriate next step. Acetabular revision is generally reserved for cases where the component is significantly malpositioned or loose, or if isolated tendon release fails.

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